#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const ll N = 1e5 + 5;
const ll mod = 1e9 + 7;
const ll inf = LLONG_MAX/5;
#define bit(x,y) ((x >> y) & 1)
vector<pair<ll,ll>> a[N];
const ll bs = 600;
ll l[N],r[N],d[N][6],b[N];
ll ans[N];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
ll k,n,m,q;
cin >> k >> n >> m >> q;
ll i,j;
for(i = 1;i <= m;i++)
{
ll u,v,t;
cin >> u >> v >> t;
u++;
v++;
a[v].push_back({u,t});
}
for(i = 1;i <= n;i++)
{
for(j = 0;j < k;j++) d[i][j] = inf;
}
ll n2 = 0;
for(i = 1;i <= n;i += bs)
{
l[++n2] = i;
r[n2] = min(n,i + bs - 1);
for(j = l[n2];j <= r[n2];j++)
{
b[j] = n2;
}
}
for(i = n2;i >= 1;i--)
{
for(j = 0;j < k;j++) d[l[i] + j][j] = 0;
for(j = l[i];j <= r[i];j++)
{
ll x = j;
for(auto tmp : a[x])
{
ll y = tmp.first;
ll add = tmp.second;
for(ll o = 0;o < k;o++) d[x][o] = min(d[x][o],d[y][o] + add);
}
}
}
for(i = 1;i <= n;i++) ans[i] = inf;
vector<ll> del;
while(q--)
{
ll s,e;
cin >>s >> e;
s++;
e++;
if(b[s] == b[e])
{
ans[s] = 0;
del.push_back(s);
for(i = s + 1;i <= e;i++)
{
del.push_back(i);
for(auto tmp : a[i])
{
ll y = tmp.first;
ll add = tmp.second;
ans[i] = min(ans[i],ans[y] + add);
}
}
}else
{
ans[s] = 0;
del.push_back(s);
for(i = s + 1;i <= r[b[s]];i++)
{
del.push_back(i);
for(auto tmp : a[i])
{
ll y = tmp.first;
ll add = tmp.second;
ans[i] = min(ans[i],ans[y] + add);
}
}
for(i = b[s] + 1;i < b[e];i++)
{
for(j = l[i];j < l[i] + k;j++)
{
del.push_back(j);
for(auto tmp : a[j])
{
ll y = tmp.first;
ll add = tmp.second;
ans[j] = min(ans[j],ans[y] + add);
}
}
for(j = r[i] - k + 1;j <= r[i];j++)
{
del.push_back(j);
for(ll t = 0;t < k;t++)
{
ans[j] = min(ans[j],d[j][t] + ans[l[i] + t]);
}
}
}
for(i = l[b[e]];i <= e;i++)
{
del.push_back(i);
for(auto tmp : a[i])
{
ll y = tmp.first;
ll add = tmp.second;
ans[i] = min(ans[i],ans[y] + add);
}
}
}
if(ans[e] == inf) cout << -1;
else cout << ans[e];
cout << "\n";
while(del.size() > 0)
{
ans[del.back()] = inf;
del.pop_back();
}
}
}
